Marine Weather Net

Straits of Florida from west end of Seven Mile Bridge to south of Halfmoon Shoal out 20 to 60 NM Marine Forecast


OVERNIGHT

THURSDAY

WNW
WINDS
5 - 10
KNOTS

THURSDAY NIGHT AND FRIDAY

W
WINDS
5 - 10
KNOTS

FRIDAY NIGHT

N
WINDS
10 - 15
KNOTS

The Marine Weather Forecast In Detail:
GMZ074 Forecast Issued: 1008 PM EDT Wed Apr 08 2020

Overnight...Mainly West To Northwest Near 5 Knots. Seas Around 1 Foot.
Thursday...Mainly West To Northwest Winds 5 To 10 Knots. Seas Around 1 Foot.
Thursday Night And Friday...Mainly West Winds 5 To 10 Knots. Seas Around 1 Foot.
Friday Night...North Winds 10 To 15 Knots, Becoming Northeast To East And Decreasing To 5 To 10 Knots. Seas 1 To 2 Feet.
Saturday...East Winds Increasing To 10 To 15 Knots. Seas 1 To 3 Feet.
Saturday Night...Southeast Winds 15 To 20 Knots. Seas Building To 3 To 4 Feet.
Sunday...Southeast Winds 15 To 20 Knots. Seas 4 To 6 Feet.
Sunday Night...Southeast To South Winds 15 To 20 Knots. Seas 3 To 5 Feet.
Monday...Southeast To South Winds Decreasing To 10 To 15 Knots. Seas 2 To 4 Feet. Slight Chance Of Showers.
Monday Night...South Winds 10 To 15 Knots. Seas 2 To 4 Feet. Isolated Showers.
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Synopsis for Keys coastal waters from Ocean Reef to Dry Tortugas: GMZ005
1008 PM EDT Wed Apr 8 2020

A diffuse high pressure ridge will nose in from the Atlantic and into the Straits of Florida through Thursday night. The ridge to our south will dissipate Friday. High pressure will zip across the Southeast States Friday night, heading east into the Atlantic on Saturday on its way to Bermuda. Strong low pressure will develop over the Lower Mississippi Valley on Sunday, bringing freshening southeast and south breezes.

Gulf Stream
The Approximate Shoreward Edge of the Gulf Stream as of April 9...
- 40 NM South of Dry Tortugas Light...on Loggerhead Key.
- 13 NM South of Cosgrove Shoal Light...off the Marquesas Keys.
- 6 NM South of Sand Key Light...off Key West.
- 3 NM South of Looe Key...off Big Pine Key.
- 6 NM South of Sombrero Key Light...off Marathon.
- 15 NM Southeast of Alligator Reef Light...off Islamorada.
- 15 NM Southeast of Molasses Reef Light...off Key Largo.
- 4 NM East of Carysfort Reef Light...off Ocean Reef.
Area Forecast Discussion
National Weather Service Key West FL
1034pm EDT Wednesday April 8 2020

High pressure aloft and at the surface dominates our weather this evening. A 500 mb high over the northwest Caribbean comes with a flat ridge over the southern Gulf, with the 00z KEY sounding observing a 500 mb height of 5900 meters. Meanwhile, an east- west surface ridge axis is located along the north coast of Cuba. With so much high pressure, the subsidence inversion in the evening sounding was near an uncommonly low 1,300 feet MSL. This barely even gives clouds a chance to form.

The upper ridge will weaken some on Thursday and Friday, but the surface ridge will not go far. Even if the subsidence inversion lifts a few thousand feet, it will still not deepen the mixed layer enough to generate showers. Indeed, Saturdaypm is the first time with so much as a 10 Probability of Precipitation in the forecast. Dry season continues. Otherwise, the sunny skies, light winds, and warm air aloft will support well above normal temperatures. High temperatures in the upper 80s should become increasingly common through Saturday.

Marine
Light westerly flow will prevail through Friday night, thanks to an Atlantic high pressure ridge near the north coast of Cuba. Westerly flow is known for locally accelerating during the late afternoon and early evening around the southern tip of the Florida Peninsula, bringing a surge of 15-knot winds from Florida Bay across the Upper Keys to Carysfort Light. That will be the case on Thursdaypm and Friday PM.

Winds will more broadly freshen and veer more southerly Saturday and Saturday night as low pressure deepens across the Mississippi Valley. As a result, a Small Craft Advisory may become necessary for portions of the waters over the weekend. Thereafter, winds will slacken as the aforementioned low pulls away from the region.

NOAA Key West FL Office: Watches - Warnings - Advisories
FL...None. GM...None.